bobby

ok, when i start up my car when its been sitting for a long time and i go to start it up, it will start right up and then the rpms will drop real low like have a HUGE cam in it then they will come back up and it runs perfect. whats causing this!!?!??!?! i replaced the IAC, new o2's, tune up will all aftermarket stuff listed in my sig. thanks a lot!

bobby

ANYONE???????? please

Redline03GT

Dude thats typical of cars when its a cold start up. Thats why you gotta give it a minute before you drive off...

bobby

hmmm.. i dont know of any other cars or stangs that do that, its not suppose to, its is like RIGHT ON THE EDGE of dying, then it barely comes back, it like falls to 450 rpm.

nemethjames1

redline, thats so not true... every stock car ive seen, right when you start it it will go to like 1400 OR SO and slowly go down and down til it gets to the warm idle... maybe your TPS? i'd check those first , also theres a sensor that communicates with the computer to tell it how warm the engine is, maybe you should replace that, i had a prob where durring the middle of warm up, it would die on me, then i replaced it, and it was all good.... was like a 10 dollar part... couldnt hurt, but other then that i couldnt say, hope that helps

roundman

agree with ^^^^^ check the engine temp sensor output and see if it changes as the car warms up. if it don't, then replace it and see if this doesn't cure the problem. the sensor for the engine temp to the ECU in mounted in the small pipe going to the heater core, it ain't the one in the intake near the front, this one just goes to the instrument panel temp gauge.

bobby

thanks! well i go buy an engine temp sensor and see how that works, the tps is set right where it should be. where excactly is the heater core hose at and this sensor?

roundman

on my 5.0 engine if you look at the front of the upper intake above the water pump you will see a black steel tube running diagonally from right to left and under the throttle body where a hose comes off the back of it that goes into the heater box on the passenger side. before this tube goes under the TB, there is a fitting in it with a sensor with a wire connector on it. that is the engine temp sensor that communicates with the ECU. that's the one you want to change out with a new one. drain a little from the radiator so you don't spill coolant all over the place when you remove it. it screws right out and use some teflon tape or other thread sealer on the new one when you put it in. reconnect the wires and then disconnect the negative battery cable to let the ECU reset it's memory and this should take care of changing it. let me know is this is what was wrong too as I'm just making an educated guess about it being bad!
if you want to, you could check it before you change it. backprobe the wire connector until you see some voltage on it, then start the engine and see if the voltage changes as the engine heats up. if should change, if it don't, then the sensor is bad and needs changing. if the voltage does change, then it ain't bad, so then I don't know what to do!

bobby

ahahhaa, thanks a lot Roundman! Im thinkin that what it is, i was talking to my friend and he whowed me a pictutre of it on the car so i know EXCACTLY where it is. The last question i have..... i know this sends an engine temp reading to the ECU.... as the engine gets hotter what does the ECU do to componsate for it? send less fuel and more air? THANKS A LOT once again man. (p.s. bare with me im only 15 and still learnin, LOL)

bobby

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